System, method, and computer program product for media publishing request processing

ABSTRACT

A system, method, and computer program product for publishing transcoded media content in response to publishing service requests from end users. A user request for media content, is processed intelligently, either by directing the processing of the request to one of a set of transcoding servers so as to effectively balance the load among the servers, or by directing the processing of the request to an appropriate alternative means for satisfying the request. Transcoding tasks can be prioritized. Moreover, the current load on any particular transcoding server can be monitored in conjunction with determination of the load to be created by a transcoding task, in order to facilitate server selection. Transcoding can be performed on-demand or in a batch mode. Alternatively, a request can be satisfied by distributing media content that has already been transcoded and is resident in cache memory in anticipation of such requests.

This is a continuation of application Ser. No. 12/771,599, flied Apr.30, 2010, which is a continuation of application Ser. No. 11/586,133,filed Oct. 25, 2006, now U.S. Pat. No. 7,912,893, which is a divisionalof application Ser. No. 10/076,090, filed Feb. 15, 2002, now U.S. Pat.No. 7,155,475, the entirety of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention described herein relates to publication of media contentthrough a computer network.

Related Art

The popularity of the World Wide Web (“Web”) and services provided onthe Web has increased the demands placed upon Web sites. Server farmsmade up of a number of servers are sometimes used to provide computingpower for a Web site. The load capacity on a single Internet Protocol(IP) based application server such as a Web server is often fixed. Whena load upon a server reaches a certain level, performance of the servercan degrade.

Therefore, given a server farm, load balancers can be used to distributecomputing work load across different servers. FIG. 1 shows an exampleconventional load balancer 100 coupled to a server farm 110. Server farm110 has multiple Web servers 120, 130 and 140. Load balancer 100processes requests made by Internet users 105. Load balancer 100 ismanually configured with a list of candidate Web servers 120-140 in agiven pool, each with their respective resources. Load balancer 100 canthen distribute client requests in a round-robin fashion among theavailable Web servers 120-140.

Load balancer 100 has a number of limitations. First, load balancer 100does not discriminate among requests. All requests are handled equallyregardless of whether a particular request involves more complexcomputing or a higher workload, relative to other requests. Treating ahigh workload request in the same manner as a low workload request cancreate an imbalance across servers. Second, load balancer 100 can managemultiple unrelated pools of servers, but is not aware of the data flowbetween pools of servers. This hampers load management. Third, theconfiguration needed in load balancer 100 can make it difficult toretire or reassign servers frequently or automatically. Operatorintervention may be required, since the retiring or reassignment of aserver must generally be carefully synchronized with changes on theload-balanced machines.

Load balancer 100 generally has a limited fault tolerance, based only onserver availability. Load balancer 100 may perform a TCP-level check onthe availability of Web servers 120-140 and distribute requests toavailable Web servers. This distribution (based on availability) isfairly crude and does not take into account whether an available servercan provide a useful service in light of a particular task.

Conventional load balancers are generally limited by a lack ofunderstanding of higher layer operations being carried out by servers.For example, many conventional load balancers work at a transport layer(OSI Layer 4) using TCP. At this layer, a load balancer can onlydetermine that a server is willing to accept a connection, but notwhether the server can satisfy a given request sent on that connection.

Moreover, a request from a user may not require the attention of aserver in farm 110. Alternatives may exist for the satisfaction of auser request. A server external to farm 110 may best be able to handlethe request, for example. Alternatively, a request for data could behandled by reading the requested data from a memory unit, such as acache, and delivering the data to the user. In either of these cases,the processing of one of the servers 120-140 is not necessary.

Therefore, a need exists for a system that can intelligently process auser request, either by directing the processing of the request to oneof a set of servers so as to effectively balance the load among theservers, or by directing the processing of the request to an appropriatealternative means for satisfying the request.

SUMMARY OF THE INVENTION

The inventors have recognized that limitations in conventional loadbalancers make them unsuitable for handling certain tasks, particularlythose related to on-demand media transcoding. Transcoding servers anddistribution servers that carry out on-demand media transcoding andpublication involve complex server resources that require sophisticatedbalancing of transcoding tasks on the fly. What is needed is a methodand system for intelligently processing a user request for mediacontent, either by directing the processing of the request to one of aset of transcoding servers so as to effectively balance the load amongthe servers, or by directing the processing of the request to anappropriate alternative means for satisfying the request.

The present invention is directed to a system, method, and computerprogram product for publishing transcoded media content in response topublishing service requests from end users. The topology of the systemis illustrated generally in FIG. 2. A network 201 (such as an intranetor the Internet) connects an end user 215 to a publishing service farm210. The publishing service farm 210 receives a publishing servicerequest from a client machine of end user 215. The publishing servicerequest identifies the desired media content and can include, but is notlimited to, one or more of the following constraints: formats supportedby the client, bit rate of the client connection, client player version,client locale (country of residence), client native language, requestedheight and/or width of a display window (e.g. 320×240 pixels), etc.Publishing service farm 210 processes a publishing service request byarranging and executing the delivery of the desired media content. Thiscan include transcoding of the media content into a format usable by theintended destination client. The destination client can be that of theoriginal end user 215; alternatively, the destination client can be thatof another user.

Note that the requested content originates as source media content froman origin server of a publisher such as CNN (publisher 217) or PBS(publisher 225). At the time of a publishing service request, the sourcemedia content may or may not reside at a publisher's origin server. Thesource media content may reside at a server at publishing service farm210 at the time of the request, or may reside somewhere else reachableby publishing service farm 210.

Source media content can be any digital media content including but notlimited to audio, video, streaming video, streaming audio, movies, videoclips, playlists, pointer files, metafiles, HTML pages, etc. Transcodedmedia is media content that has been transcoded from a source formatinto a destination format suitable for a client of end user 215. Thepublishing service farm 210 can, as necessary, perform this transcodingof the source media content. In one example, not intended to limit thescope of this invention, the source media content would have thefollowing properties:

video encoding: MPEG2,

audio encoding: MPEG2,

data rate: 1.6 megabits per second,

image size: 320×340 pixels,

video content: talking head,

audio content: voice.

The destination format would have the following properties:

video encoding: windows media 8,

audio encoding: windows media 8,

data rate: 300 kilobits per second,

image size: 160×120.

In particular, as shown in FIG. 3, a publishing service requestprocessor 310 at publishing service farm 210 receives a client'spublishing service request and generates an associated media providerrequest. A media provider farm 330, also at publishing service farm 210,receives the media provider request from the publishing service requestprocessor 310 and arranges for publication of media content to fulfillthe media provider request

In an embodiment of the invention, the media provider farm 330 comprisesa media provider request processor 340, a plurality of transcodingservers 350, a plurality of distribution servers 360, and a cache memory370. The publishing service request processor 310 generates a mediaprovider request to media provider request processor 340 in the mediaprovider farm 330. The media provider request specifies one of severaltypes of processing, depending on the media content requested, theconstraints of the client, and resources available to the media providerfarm. First, the media provider request can specify on-demandtranscoding, in which source media content is transcoded by one ofseveral transcoding servers 350 in the media provider farm 330, toproduce the media content in the requested format. The transcoded mediacontent is then sent to a destination client through a distributionserver 360 in the media provider farm. Second, the media providerrequest can specify a cache access, so that previously transcoded mediacontent, resident in the cache 370 in the media provider farm 330, canbe used to fulfill the client's publishing service request. Again, thetranscoded media content is sent to the destination client through adistribution server 360 in the media provider farm 330. Third, the mediaprovider request can specify pass-through processing, in which therequesting client is directed to an origin server (not shown) from whichthe requested media content can be provided directly.

An embodiment of the invention also allows for transcoding independentof any particular client or user. Here, a media provider requestscheduler 320 creates and sends a batch media provider request to themedia provider request processor 340, specifying the source mediacontent to be transcoded and a format. Like a media provider requestmade in the on-demand mode, such a request generated in the batch modecan include, but is not limited to, one or more of the followingconstraints relevant to clients: client media format, bit rate of theclient connection, client player version, client locale (country ofresidence), client native language, requested height and/or width of adisplay window (e.g. 320×240 pixels), etc. As in the case of on-demandtranscoding, a transcoding server 350 transcodes the media content(obtained from an origin server) in the specified format. The resultingtranscoded media content is then cached, in anticipation of futurepublishing service requests from end users.

When a transcoding task is to be performed in the media provider farm(i.e., in the on-demand and batch cases), the invention provides aprocess for selecting a transcoding server. The process seeks to selecta particular transcoding server in a manner that balances the totalityof ongoing transcoding tasks across all such servers. The processconsiders the processing load that will be created by the transcodingtask and the current load being borne by each transcoding server.According to one embodiment of the invention, the media provider requestprocessor has a detailed understanding of the application layer (OSIlayer 7) including application(s) performed by each type of transcodingserver. This understanding is used to allocate transcoding tasks suchthat the work of servers is balanced more effectively. For example,unavailable servers are culled more effectively. This in turn provides abetter quality of service to the end user. According to a furtherfeature, the media provider request processor can even understand andbalance transcoding servers which do not implement an industry-standardprotocol like HTTP.

In an embodiment of the invention, each transcoding task is assigned apriority that can be based, for example, on the number of viewersseeking the associated media content. A higher priority transcoding taskwill displace a task of lower priority. The lower priority task can be“killed.”

Additional features and advantages of the invention will be set forth inthe description that follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives ad other advantages of the invention will be realized andattained by the system and method particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of a preferredembodiment of the invention, as illustrated in the accompanyingdrawings:

FIG. 1 illustrates the operation of a conventional load balancer.

FIG. 2 illustrates the general system of an embodiment of the invention.

FIG. 3 is a block diagram illustrating a publishing service farm,according to an embodiment of the invention.

FIG. 4A is a block diagram illustrating the system of the invention asit processes an on-demand media provider request, according to anembodiment of the invention.

FIG. 4B is a block diagram illustrating the system of the invention asit processes a cached media provider request, according to an embodimentof the invention.

FIG. 4C is a block diagram illustrating the system of the invention asit processes a pass-through media provider request, according to anembodiment of the invention.

FIG. 4D is a block diagram illustrating the system of the invention asit processes a batch transcoding media provider request, according to anembodiment of the invention.

FIGS. 5A and 5B collectively illustrate the processing of a publishingservice request by either cache access or on-demand transcoding,according to an embodiment of the invention.

FIG. 6 is a flowchart illustrating the processing of a publishingservice request by pass-through processing, according to an embodimentof the invention.

FIG. 7 is a flowchart illustrating batch transcoding, according to anembodiment of the invention.

FIG. 8 is a more detailed block diagram of the system of the inventiondescription, according to an embodiment of the invention.

FIGS. 9 and 10 collectively illustrate determination of a publishingoption, according to an embodiment of the invention.

FIG. 11 is a flowchart illustrating estimation of task load, accordingto an embodiment of the invention.

FIG. 12 is a flowchart illustrating estimation of server load, accordingto an embodiment of the invention.

FIG. 13 is a flowchart illustrating speculative transcoding, accordingto an embodiment of the invention.

FIG. 14 is a flowchart illustrating the determination of serveravailability, according to an embodiment of the invention.

FIG. 15 is a flowchart illustrating the shutting down of a server,according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Table of Contents I. Overview II. System A. On-demand B. Cache C.Pass-through D. Batch E. Intelligent Publishing Agent and Load MonitorsF. Environment III Process A. On-demand and Cache Processing B.Pass-through Processing C. Batch Processing D. Determining Type of MediaProvider Request E. Estimating Task Load F. Estimating Server Load G.Speculative Batch Processing H. Zero-Downtime Reassignment of Servers toDifferent Tasks, Fault Tolerance, and Zero-Downtime Server RetirementIV. Data V. Conclusion

I. OVERVIEW

The invention described herein is a system, method, and computer programproduct that allows an end user to access media content across anetwork. In particular, the invention accepts a request from the user'sclient machine and sends the requested media content to a destinationclient in a format that is usable in light of the destination client'sconfiguration. Note that the requesting client and the destination mayor may not be the same machine. The requested media content in itsoriginal form (denoted herein as source media content) may be of adifferent format than what is desired or required by the end user. Inthis situation, the source media content is transcoded, by transcodingservers, into a format usable by the user at the destination client. Insome situations, the requested media content will have already beentranscoded and stored in a cache. In such a case, the already transcodedmedia content is simply distributed to the client. In other cases, ifthe source media content is already in an appropriate format for the enduser, the transcoding process will effectively be bypassed, so that theclient is simply directed to the origin server on which the source mediacontent resides.

Source media content may originate from a storage device or anotherdistribution server. The storage device or server may reside at anynetwork location reachable by the transcoding servers. For example, thestorage device or server may be housed in the same facility as thetranscoding servers, or it may reside elsewhere on the Internet. Thesource media content may be stored (pre-recorded), or it may consist oflive content being digitized as it is being distributed.

One or more transcoding servers can be used to transcode source mediacontent into a format usable by the user at the destination client. Theinvention includes a process by which the load placed on the transcodingservers is generally balanced. This facilitates efficient usage ofavailable transcoding capacity. In an embodiment of the invention,transcoding tasks can be prioritized, so that more important transcodingtasks are performed, while less important transcoding tasks are deferredor killed.

In some situations, it may be desirable to allow some variants of theconstraints that would otherwise be placed on a transcoding task. Suchconstraints include those related to the format requested or required bya client. “Loosening” these constraints may allow a faster or moreefficient completion of a transcoding task. This would then allow afaster response to the end user. Relaxing the constraints may also allowdelivery of the media content in a superior format than what wasrequested. Moreover, if transcoded media content is already available incache memory, such content may be provided to the client even if theformat of such material does not exactly match that specified by therequesting client.

As described in this section, and as will be seen in greater detailbelow, a number of options exist as to how a user's request for mediacontent can be filled. It is a feature of this invention, that, given arequest from an end user, all options are evaluated and an appropriateresponse is made in light of the request and the resources available forfulfilling the request.

The invention is illustrated generally in FIG. 3. This illustrates thepublishing service farm 210 introduced above in FIG. 2. A client'srequest for media content is first received by a publishing servicerequest processor 310. A request from the client, known hereinafter asthe publishing service request, contains information about the specificmedia content desired and can also contain information about theconfiguration of the client. Alternatively, publishing service requestprocessor 310 can receive information about the client's configurationduring separate communications associated with the publishing servicerequest. The publishing service request processor 310 is also aware ofthe resources that can be brought to bear in fulfilling the publishingservice request. These resources can include, for example, theavailability of transcoding capacity, and the availability of therequested media content in an already transcoded form. Based on theinformation pertaining to the client's configuration and on informationpertaining to resources available, publishing service request processor310 decides how best to fulfill the publishing service request.

Publishing service request processor 310 may, for example, determinethat source media content needs to be obtained from an origin server andtranscoded. Publishing service request processor 310 may alternativelydecide that the requested transcoded media is already available, and instorage within publishing service farm 210. In this case, the requestedtranscoded media content would simply be read from memory and providedto the destination client. Publishing service request processor 310 canalternatively decide that the requesting client should be redirected tothe origin server itself so that the desired media content can bedelivered directly from the origin server.

The specific option identified by the publishing service requestprocessor 310 is then conveyed in a media provider request to mediaprovider farm 330. In particular, the media provider request is sent tomedia provider request processor 340. If the media provider requestspecifies that a transcoding task is to be executed in response to theclient's request (i.e., “on-demand”) than media provider requestprocessor 340 initiates a transcoding task at one of several transcodingservers, such as transcoding server 350. As will be described in greaterdetail below, the selection of a transcoding server is based on thetranscoding task and on the attributes of the assorted transcodingservers. These attributes include the available transcoding capacity oneach transcoding server. In initiating a transcoding task, mediaprovider request processor 340 will also consider the load that thetranscoding task is expected to create on a transcoding server. Aneffort is made to select a transcoding server such that the totalprocessing load across all servers is generally balanced. In addition,the priority of the transcoding task can also be a factor, in that atask of higher priority will be allocated to the transcoding server bestable to execute the transcoding task in a timely manner. In anembodiment of the invention, a higher priority transcoding task candisplace a lower priority transcoding task in a manner described ingreater detail below.

If the media provider request sent by publishing service requestprocessor 310 specifies that the media provider request is to befulfilled by media content that has already been transcoded, mediaprovider request processor 340 accesses the already transcoded mediacontent from a cache memory 370. Such transcoded media content can thenbe sent to the destination client. Cache 370 is used to service requeststhat would otherwise consume transcoding resources. To facilitateaccess, the client constraints used to create the cache entry areassociated with each cache entry.

All transcoded media that is provided by media provider farm 330 to theclient is distributed to the client through one of several distributionservers, such as distribution server 360. This applies to media contentthat has been accessed from cache 370 or media content that has beentranscoded by one of the transcoding servers. Distribution is initiatedby a request from media provider request processor 340 to distributionserver 360. The selection of a particular distribution server is basedon availability and on the type of delivery service required. Forexample, in some cases a hypertext transfer protocol (HTTP) server isappropriate; in other cases, a RealServer (RTSP protocol), Windows MediaServer (MMS protocol), or QuickTime server (RTSP protocol) isappropriate. Distribution server 360, which can be a streaming ordownload server, serves transcoded media content by either streaming itor downloading it to the destination client or to another distributionserver. Examples of distribution processes include, but are not limitedto, RealNetworks Real audio/video streaming, Apple QuickTime audio/videostreaming, Microsoft Windows Media audio/video streaming, shoutcast/MP3streaming, and HTTP downloading of RealNetworks, Microsoft, QuickTime,or Generic Media gMovie player movie files.

Media provider request processor 340 can also accept media providerrequests from media provider request scheduler 320. Scheduler 320 actsautonomously from any particular client. Such a request from mediaprovider request scheduler 320 can be viewed as a pre-encode batch mediaprovider request. Based on such a request, media provider requestprocessor 340 initiates a transcoding task, resulting in transcodedmedia content that is then stored in cache 370. This results in theready availability of transcoded (pre-encoded) media content in mediaprovider farm 330, so that future publishing service requests can behandled without transcoding on-demand.

II. SYSTEM

The system of FIG. 3 will now be described in greater detail withrespect to possible operating modes. This section describes the variouslogical components of the invention and their connectivity. Theprocessing that takes place within and between the components isdescribed only briefly, in order to explain the structure of theinvention. A more detailed discussion of the processes of the inventionis presented in section III.

A. On-Demand

FIG. 4A illustrates the system of the invention as it processes anon-demand media provider request. A client 402 sends a publishingservice request to publishing service request processor 310. Publishingservice request processor 310 then sends a media provider request tomedia provider request processor 340. The media provider request in thisexample specifies an on-demand transcode. Media provider requestprocessor 340 then initiates a transcode task at a transcoding server350. Transcoding server 350 then accesses source media content 355.Source media content 355 is obtained from an origin server (not shown)on which source media content 355 resides.

Transcoding server 350 then performs the transcode task in a mannerspecified by the media provider request. The resulting transcoded mediacontent is then sent to a distribution server such as distributionserver 360. Note that in an embodiment of the invention, the transcodedmedia content is also sent to cache 370. This allows subsequentpublishing service requests from client 402 or from any other client tobe serviced by media provider farm 330 without having to repeat thetranscode task Distribution server 360 passes the transcoded mediacontent to publishing service request processor 310, which forwards thetranscoded media content to client 402, or to whatever client wasspecified in the publishing service request.

B. Cache

The system of the invention is illustrated in FIG. 4B processing apublishing service request through the use of cached media content thathas already been transcoded. Here, client 402 issues a publishingservice request to publishing service request processor 310. Publishingservice request processor 310 then evaluates the publishing servicerequest in light of what it knows about available resources. Inparticular, if publishing service request processor 310 knows that therequested media content is available in cache 370 then publishingservice request processor 310 issues a media provider request specifyingcache access. This media provider request is passed to media providerrequest processor 340.

Media provider request processor 340 then chooses a distribution server,such as distribution server 360. A distribution request is sent frommedia provider request processor 340 to distribution server 360,instructing distribution server 360 to distribute the requestedtranscoded media content from a specified file in cache 370 to theclient. The transcoded media content is then read from cache 370 andforwarded to publishing service request processor 310 through the chosendistribution server 360. The requested content is then forwarded toclient 402, or to whatever client was specified in the publishingservice request.

C. Pass-Through

The system of the invention can also operate to direct a client to anorigin server, from which the client can obtain the desired mediacontent directly. This is illustrated in FIG. 4C. Here, as before,client 402 sends a publishing service request to publishing servicerequest processor 310. Publishing service request processor 310 thendetermines that the publishing service request can best be served by anorigin server (not shown) that can provide source media content 355.This results in a media provider request being sent from publishingservice request processor 310 to media provider request processor 340.Such a media provider request specifies that the content is to beobtained by client 402 from an origin server directly. The mediaprovider request processor 340 then directs the client's media player tothe origin server.

D. Batch

In addition, the system of the invention can also perform transcoding inanticipation of future client requests. This is illustrated in FIG. 4D,and is denoted hereinafter as batch transcoding. Here, a media providerrequest scheduler 320, acting independently of any specific clients orend user, sends a media provider request to media provider requestprocessor 340. This request specifies both the source media content tobe transcoded and the format of the resulting transcoded content. Themedia provider request processor 340 then initiates a transcoding taskat a transcoding server 350. Transcoding server 350 then accepts sourcemedia content 355 and performs transcoding. The resulting transcodedmedia content is stored in cache 370. The transcoded media content isthen available for eventual distribution to requesting users via adistribution server such as distribution server 360.

E. Intelligent Publishing Agent and Load Monitors

The system illustrated in FIGS. 4A through 41) can be enhanced by anumber of modules that facilitate the operation described herein. Theseenhancements are illustrated in FIG. 8. In this embodiment, publishingservice request processor 810 includes an intelligent publishing agent812. This agent considers the utility of the various ways in which agiven publishing service request can be handled. Agent 812 will evaluatethe utility of directing the client to an origin server, as illustratedin FIG. 4C for example. Agent 812 would also consider the utility ofaccessing cache 370 in order to fulfill the publishing service request.Alternatively, agent 812 may determine that transcoding, as illustratedin FIG. 4A, is appropriate. If transcoding is chosen, agent 812 willalso decide if lower priority transcoding tasks need to be killed. Agent812 will also decide whether some of the client constraints identifiedin the publishing service request can be ignored or modified.

A media provider request is then sent from publishing service requestprocessor 810 to media provider request processor 840. If the mediaprovider request specifies that transcoding is to be performed, then atranscoding task must be initiated at a transcoding server. Tofacilitate the allocation of the transcoding task to a particulartranscoding server, the load to be placed on the transcoding server bythe particular transcoding task must be evaluated. This is the job ofthe task load monitor 844. The nature of on-demand media transcoding issuch that it is difficult to predict the load an individual task willput on the system. In the case of the transcoding servers, the load is afunction of the source media content, requested destination format, andserver hardware. Determining the resulting load is sufficiently complexthat one cannot reliably compute it before the transcode begins. This isprimarily due to the wide variety of source and destination propertiesthat the transcoding servers collectively support. In addition,variations in server hardware amongst the transcoding farm servers (CPUclock speed, hard drive performance, hardware acceleration boards, etc.)make some servers more efficient than others at certain tasks (decodesor encodes of specific formats, color coordinate transformations, etc.).

Task load monitor 844 estimates task load by constructing a model ofrequired load for a given request based on previous transcodes. Uponcompletion of any transcode, transcoding tasks record the source,destination, and server properties along with statistics on their load(e.g., average CPU load, maximum CPU load) into a database 843. Duringthe server selection process, task load monitor 844 estimates theprospective load of a requested task by comparing source, destinationand potential server properties with that of previous transcodes. If anexact properties match is found, the load of the previous matchingtranscode is used as the load estimate for the new task. If an exactmatch cannot be found, the closest properties match is used as the loadestimate for the new task. In the difference calculation, certainproperties are given more weight than others, as will be describedbelow.

In addition, the current processing load on each of the transcodingservers (i.e., load value) must be considered. One aim of the presentinvention is to maintain an accurate load value for all servers, so thatthe media provider request provider 840 does not mistakenly overload orunder utilize a server. This is the job of the server load monitor 842.Transcoding servers periodically report their load to the server loadmonitor 842. Between the time at which a task is allocated on atranscoding server and the time at which the server next reports anexisting load that includes that task, it will appear to the mediaprovider request provider 840 as if the new task has placed no loadwhatsoever on the server. One can imagine a scenario in which a task isassigned to a transcoding server, and the media provider requestprovider's load value for that server is not updated in a timely manner.The media provider request provider 840 may mistakenly assign more tasksto the server, eventually overloading it.

To overcome this race condition, server load monitor 842 tracks thestate of new tasks and assigns an estimated load to tasks until theyreach a mature, or running, state. During this time, server load monitor842 calculates the server load as the measured current server load plusthe load estimate for each of the newly allocated tasks on thattranscoding server. Once the task has reached the mature, running state,a server handling the task updates its reported state to “running” toindicate that its load is accurately reflected in the returned measuredserver load. This has the effect of reserving a portion of thetranscoding server for the new task until the task can start up andreport its actual measured load, avoiding the race condition.

In the embodiment of FIG. 8, media provider request scheduler 820includes a speculative transcoding manager 822. Manager 822 decides whatsource media content should, be transcoded in batch mode operations. Thevolume and nature of publishing service requests is not constant. Evenon a daily basis, the demand for content typically rises beginning inthe late morning, peaks in the early evening, and descends into themorning hours. Speculative transcoding manager 822 takes advantage ofotherwise idle farm time by speculatively transcoding content for lateruse.

The choice of which transcodes to perform speculatively can be motivatedin several ways:

-   -   Speculative transcoding manger 822 can optimize farm efficiency        by examining the record of previous transcoded formats, players,        etc. and speculatively transcode media clips into those formats        during off-peak times. In general this would allow a distributed        on-demand media transcoding system to support the same quality        and quantity of service with fewer transcoding servers.    -   Source content can be transcoded slower than real-time and thus        at a higher quality level than possible during an on-demand        transcode. In one business method according to the present        invention, revenue can be increased by offering such encoding as        an extra cost service to customers.

Source media content may also, for example, be transcoded to meet aschedule specified by a publisher.

F. Environment

Referring again to FIG. 2, a block diagram is shown representing anexample operating environment of the present invention. It should beunderstood that this operating environment is shown for illustrativepurposes only and does not limit the invention. Other implementations ofthe operating environment described herein will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein,and the invention is directed to such other implementations.

The illustrated operating environment includes an end user 215, originservers 217 and 225, a publishing service farm 210, and a network 201.Only one user and two origin servers are shown for clarity. In general,any number of these components can be included in the system of thepresent invention. Moreover, in FIG. 2 the origin servers are shown at apublisher's facility, external to publishing service farm 210. Note thatin other environments of the invention, an origin server may be insidepublishing service farm 210 or somewhere else reachable by publishingservice farm 210.

The end user 215, the origin servers 217 and 225, and the publishingservice farm 210 are all connected via a network 201. The network 201connects all the components of the present invention, and can be anytype of computer network or combination of networks including, but notlimited to, circuit switched and/or packet switched networks, as well aswireless networks. In one example, the network 201 includes theInternet.

Any conventional communication protocol can be used to supportcommunication between the components of the system. For example, aTransmission Control Protocol/Internet Protocol (TCP/IP) suite can beused to establish links and transport data and Real-Time StreamingProtocol (RTSP) can be used to stream data between components of thesystem. A World Wide Web-based application layer and browser (and Webserver) can also be used to further facilitate communication between thecomponents shown in FIG. 2. However, these examples are illustrative.The present invention is not intended to be limited to a specificcommunication protocol or application, and other proprietary ornon-proprietary network communication protocols and applications can beused. The user 215, or viewer, uses a client machine to request mediacontent via the network 201, and/or to play received media content. Inembodiments of the invention, the destination client is a personalcomputer that includes a Web browser and one or more media playersrunning under the computer operating system. Alternately, thedestination client can be a WEBTV, a WINDOWS CE device, a PersonalDigital Assistant (PDA), a PALM handheld device, a console appliancewith network access capability, an MP3 appliance, or any other clientdevice and/or program capable of requesting, receiving and/or playingmedia content. However, the invention is not limited to these examples,and one skilled in the art will appreciate that a wide variety of clientdevices and programs can be used to request, receive and/or play mediacontent via the network 201. The invention is directed to such otherclient devices and programs.

The destination client is capable of receiving and playing various typesof media content. For example, the user client may receive and/or playmedia content in various well-known encoded formats including, but notlimited to, MPEG, AVI, MP3, REAL, WINDOWS MEDIA, QUICK TIME, H.263 videocoding, and PALM-compatible formats.

The origin servers 217 and 225 are used by their respective contentproviders to publish and/or transmit media content over the network 201.An origin server can provide media content using a variety of mediainput devices and programs. For example, media content can be providedusing cameras (8 mm, Hi-8, or any video digitizing device),line-in/microphone (either attached to any of the camera devices, orstand-alone audio input devices), digital cameras, devices that uploadslide shows with voice-over illustrations, files previously encoded in aclient-chosen format, or files available via a network accessible mountpoint (such as, but not limited to, Hypertext Transfer Protocol (HTTP),File Transfer Protocol (FTP), or remote servers). These examples are notlimiting, and one skilled in the art will appreciate that a wide varietyof client devices and programs can be used to publish and/or transmitmedia content via the network 201, and that the invention is directed tosuch client devices and programs.

An origin server is capable of publishing and/or transmitting varioustypes of media content. For example, the origin server 217 can providemultimedia files in various well-known encoded formats including, butnot limited to, MPEG, AVI, MP3, REAL, WINDOWS MEDIA, QUICK TIME, H.263video coding, and PALM-compatible formats.

The publishing service farm 210 acts as an intermediate between theorigin servers and the user client 215. As will be described in moredetail below, the publishing service farm 210 receives requests formedia content from the user client 215 and obtains the requested mediacontent from an origin server. If necessary, the publishing service farm210 then transcodes the media content received from the origin serverfrom a source type to a destination type that can be accommodated by theuser client 215, and delivers the transcoded media content to the userclient 215 or other destination client. The publishing service farm 210performs the transcoding and/or delivery of the requested media contentin a manner that is transparent to the content provider as well as theviewer of the media content.

In accordance with the present invention, because the publishing servicefarm 210 can distribute media content in a variety of formats, i.e.,destination types, the origin server can provide media content using asingle media input device and still deliver the content to viewers usinga variety of media players, each of which requires a differentdestination type. Additionally, the present invention permits users toaccess a variety of media content published in different source types nomatter what media player they are using.

III. PROCESS

A. On-Demand and Cache Processing

One process for handling a client's publishing service request isillustrated in FIG. 5A. In step 510, the client's publishing servicerequest is received at a publishing service request processor. Assumingthat pass-through processing is not appropriate in this case, in step515, the publishing service request processor determines whether therequested media is available in the cache memory of the media providerfarm. If so, then in step 520, the publishing service request processorgenerates and sends a cached media provider request to the mediaprovider request processor. The media provider request processor thenselects a distribution server in step 522. In step 524, a distributionrequest specifying the desired content is sent to the selecteddistribution server. In step 526, the desired transcoded media contentis delivered from the cache to the client via the selected distributionserver. Note that in an embodiment of the invention, the transfer oftranscoded media content from the cache to the client is pipelined, sothat content is distributed to the client as it is transferred from thecache. In such an embodiment, it is not necessary, therefore, for thedistribution server to receive all the requested content from the cachebefore starting distribution. Rather, distribution proceeds as thecontent becomes available at the distribution server, and as the rest ofthe requested content continues to be transferred from the cache.

Note that here, and in all other situations in which media content isdistributed using this invention, the media content may be sent to aclient other than that of the end user that originated the publishingservice request. The receiving client will be specified in thepublishing service request.

If, in step 515, the determination is made that the requested media isnot available in cache memory, then processing continues at step 530. Inthis step, the publishing service request processor determines whetherthere is transcoding capacity available in the media provider farm. Ifnot, then the end user is informed that the system is too busy toprocess the request. If, however, capacity is available, then processingcontinues at step 532. Here, the publishing service request processorgenerates and sends an on-demand media provider request to the mediaprovider request processor. Referring to FIG. 5B, in step 540, thedeterminations are made as to the processing load inherent in thetranscoding task, the current load on the transcoding servers, and thepriority of the transcoding task. These determinations are described ingreater detail below: In step 541, a specific transcoding server isselected by the media provider request processor. In step 542, the mediaprovider request processor selects a distribution server. In step 544, atranscoding task is initiated at the selected transcoding server by themedia provider request processor, directing the selected transcodingserver to transcode and send its media content output to the selecteddistribution server. In step 546, a database is updated as to the statusof the transcoding task. In an embodiment of the invention, thisdatabase resides at the media provider request processor and records thestatus and maturity of the transcoding task for purposes of informingsubsequent decisions as to server selection. For an immature task, anestimate of the processing load of the task can be recorded at thedatabase.

Note that in processing any given media provider request, theavailability of transcoding servers must be determined accurately andunambiguously. If, for example, two media provider requests are beingprocessed more or less simultaneously, there is a risk that each requestwould be unaware of the prospective processing load implied by theother. This could result in a resource contention problem, where eachmedia provider request could lay claim to the same transcoding server.To prevent conditions such as these, database access must be controlled.In one embodiment of the invention, a media provider request is grantedexclusive access to the database for purposes of determining server load(step 540) while other pending media provider requests wait. When thetask and load associated with the first request have been assigned to aserver, then the processing of another media provider request can beginby determining the current server load, etc. This and other mechanismsfor preventing resource contention and database coherency problems areknown to persons of skill in the art.

In step 550, the selected transcoding server transcodes source mediacontent to obtain the media content that was requested by the client'spublishing service request. In step 552, the resulting transcoded mediacontent is sent to the selected distribution server. Note that in anembodiment of the invention, the transcoded media content is also sentto cache memory, where it is stored in the event that subsequentpublishing service requests seek the same transcoded media content. Instep 553, the database is updated to reflect completion of transcoding,and to record historical data relating to the transcode, such asprocessing load statistics, and source, destination, and transcodingserver properties. This data can be used subsequently in estimating theload that will be required for future, similar tasks. In step 554, adistribution request is sent to the selected distribution server. Instep 560, the transcoded media content is delivered from the selecteddistribution server to the destination client.

Note that steps 550 through 560 are shown in FIG. 5B as discrete eventsthat occur in serial. In an alternative embodiment of the invention,these events are pipelined, so that as media content is transcoded, thetranscoded media content is sent to a distribution server, whiletranscoding of the remaining source media content continues. It istherefore not necessary that the entire transcoding task finish beforethe transcoded media content is sent to the distribution server.Similarly, distribution can take place as transcoded content becomesavailable from the transcoding server. Distribution can proceed even astranscoded media content continues to be transferred to the distributionserver. In another alternative embodiment of the invention, thetranscoding server writes transcoded media content to the cache, and oneor more distribution servers reads the transcoded media content from thecache as additional content is being generated.

B. Pass Through Processing

In the event that the publishing service request processor decides thatthe publishing service request should be handled in a pass, throughmanner, the resultant processing takes place as illustrated in FIG. 6.In step 610, a publishing service request is received from therequesting client. In step 630, a corresponding media provider requestis sent to the media provider request processor. As a result, the mediaprovider request processor directs the requesting client to the originserver that serves the requested the media content

C. Batch Processing

As described briefly above, the invention can also perform batchtranscoding independent of any particular client or publishing servicerequest. The process for batch transcoding is illustrated in FIG. 7. Instep 710, a batch media provider request is received at the mediaprovider request processor from the media provider request scheduler.Note that in the illustrated embodiment, batch requests are made onlywhen the necessary resources are available at the media provider farm.In step 715, determinations are made as to the processing load that thetranscoding task will create at a transcoding server, the current loadon the transcoding servers, and the priority of the task. In step 720,the media provider request processor selects a particular transcodingserver. In step 730, a transcoding task is initiated at the selectedtranscoding server by the media provider request processor. In step 735,the database is updated as to the status of the transcoding task. Instep 740, the selected transcoding server transcodes the media contentidentified in the media provider request. In step 745, the database isupdated to reflect completion of transcoding, and to record historicaldata relating to the transcode, such as processing load statistics, andsource, destination, and transcoding server properties. This data can beused subsequently in estimating the load that will be required forfuture, similar tasks. As discussed above, database coherency must bemaintained, so that any process that accesses the database receivesaccurate information. For this reason, steps must be taken to ensurethat updates to the database (e.g., steps 735 and 745) are completedbefore permitting any attempts to read the data. In step 750, theresulting transcoded media content is stored in cache memory. Asdescribed above, a publishing service request processor can generate anyone of several media provider requests to the media provider requestprocessor. Such a request, may specify pass through processing, cacheaccess, or on-demand transcoding.

D. Determining Type of Media Provider Request

The process of determining what kind of media provider request togenerate (and, therefore, what kind of request processing to perform) isillustrated in FIG. 9. In step 910, the publishing service request isreceived at the publishing service request processor from a client. Instep 920, the optimum publishing option is determined, based on realtime information regarding the condition of the media provider farm andon the request itself. The relevant information on the condition of themedia provider farm includes the availability of transcoding servers andthe availability of the requested transcoded media in cache memory. Instep 930, a media provider request is generated, specifying the optimumpublishing option. In step 940, the media provider request is sent tothe media provider request processor.

Steps 920 and 930, the steps of determining the optimum publishingoption and generating the corresponding media provider request,respectively, are illustrated in greater detail in FIG. 10. With respectto step 920, an evaluation of step 1010 takes place, in which options1020 through 1070 are considered. Option 1020 represents publicationbased on a match between the requested media content and cache contents.Option 1030 represents publication based on a near match between therequested media content and the cache contents. In this case, therequested media content is present in cache, but not in the requestedformat. If the format of the cached media content is close to what isrequested, it may be more practical to distribute the cached contentrather that perform a transcode.

Option 1040 represents publication based on an on-demand transcodeoperation wherein the transcoding matches the constraints identified inthe publishing service request. Option 1050 also represents publicationbased on a transcode operation wherein the transcoding matches theconstraints identified in the publishing service request. In option1050, however, the transcode task has a certain priority that is thencompared with the priorities of ongoing transcoding tasks. Option 1060represents publication based on a transcode operation wherein theconstraints identified in the publishing service request are varied, sothat the originally identified constraints are not matched exactly intranscoding. Option 1065 also represents publication based on atranscode operation wherein the originally identified constraints arenot matched exactly in transcoding. Like option 1050, however, option1065 includes assessment of the priority of the transcoding taskrelative to other ongoing tasks. Option 1070 represents publicationbased on a pass through operation. In step 1080, the ideal option isselected.

With respect to step 930, generation of the appropriate media providerrequest is performed in step 1090. The generated request will be one ofrequests 1091 through 1099. Media provider request 1091 specifies cacheaccess and corresponds to publishing option 1020.

Media provider request 1092 specifies cache access wherein the accessedmedia content represents a near match of the contents requested in thepublication service request. Request 1092 corresponds to publicationoption 1030. When all attempts at scheduling new transcoding tasks havebeen exhausted it is possible, in this case, to respond to the clientrequest with a piece of cached transcoded media that closely, but notexactly, matches the original request. Most users would rather see theirrequest serviced with slightly modified constraints than not at all.

Here, existing cached transcoded media is sorted based on weight, wheretheir weight is a function of their associated request constraint'svariance from the client's original request constraints. More weight isgiven to constraints of greater importance, such as the source mediacontent, player type, and player version. Less weight is given toconstraints of less importance such as bitrate, height, width, etc. Thecache entry of least weight variance is returned to the client. If theminimum variance is sufficiently large (e.g. no transcode of aparticular source media within an acceptable variance could be found inthe cache), option 1092 will not be chosen.

There may be some circumstances under which previously transcoded mediacontent will be chosen, where the chosen media content does not exactlymatch the client's constraints, even when there is enough spare capacityto launch a new transcoding task that exactly matches the client'sconstraints. One example where this may occur is if previouslytranscoded media exists that has been transcoded in non-real-time as inthe case of speculative transcoding operations; its quality may be somuch higher than the real-time transcode that could be produced with anexact constraint match, that the previously transcoded media willprovide an overall superior experience for the end user.

Returning to FIG. 10, media provider request 1093 specifies on-demandtranscoding, and corresponds to publication option 1040. Media providerrequest 1094 specifies on-demand transcoding, wherein on-goingtranscoding tasks of lower priority can be killed to allow processing ofthe current transcoding task. The kill command 1095 is incorporated withrequest 1094. Request 1094, along with command 1095, correspond topublication option 1050.

Killing a task is based on priority. Each task is responsible forperiodically updating its own entry in a table of tasks and respectivepriorities, providing both load and priority information. Task priorityis determined by several factors including number of viewers (sincecontent in high demand makes for a more urgent task) and contractedpublisher uptime (since an obligation to publish also makes a task moreurgent). Transcoding servers handling transcoding tasks actively modifya task's priority when the number of viewers changes. In the simplestcase, a transcoding task whose viewer count has fallen to zero lowersits priority. If a new user joins, the server handling a task raises itspriority.

Determination of which task(s) to kill is accomplished by iteratingthrough the servers of the needed type until a server is foundcontaining a set of lower priority tasks whose total load is less thanthe load estimate of the new task to be initiated. Once a server with aset of killable tasks has been identified, the media provider requestprocessor sends kill message(s) to the identified killable tasks, thenallocates the new task to the selected server. Note that the mediaprovider request processor can kill tasks on transcoding and/ordistribution servers, as needed.

In one example not intended to limit the scope of the invention, atranscoding task A is spawned in response to a request A. Initially itis assigned a priority of I because it has a single viewer. If, forexample, the viewer disconnects, then the priority is lowered to zero toindicate lack of viewers. As task A proceeds, it reports an associatedload of 50 units. Given a new task B with an estimated load of 40, themedia provider request processor might then search for a transcodingserver with a set of tasks of lower priority than B's priority, whosereported load is greater than or equal to 40. In this case, the mediaprovider request processor will find that server A and task A satisfyits search. The media provider request processor reserves task B'sestimated load on the server, then issues a kill command to task A,followed by initiation of task B at server A.

Media provider request 1096 specifies on-demand transcoding, wherein theconstraints identified in the publishing service request can be varied.Request 1096 corresponds to publication option 1060. Such a mediaprovider request may be appropriate, for example, when matching arequested format exactly is less important than a timely response. If,for example, none of the other options are feasible, then option 1096could be the only alternative that satisfies the request. In the case ofoption 1096, the request is fulfilled in a slightly different formatthat what was requested. Alternatively, media content of a qualityhigher than what was requested may be provided. Again, matching therequested format exactly would be a secondary consideration. Note thatby providing option 1096, system efficiency is enhanced, since thenumber of unique sets of constraints serviced by the system is reduced.This can allow the use of fewer transcoding servers by increasing theprobability that a request can be handled by a cache.

In one example not intended to limit the scope of the invention, atranscoded task (with a requested bit rate of 300 k) has an estimatedload of 80 units, but at most only 60 units of load are available on anyparticular transcoding server. In this case the media provider requestprocessor could conform the estimate load to the available load byreducing the requested output bit rate from 300K to 128K. The mediaprovider request-processor next determines if this optimization iswithin the acceptable variance of the original request. In this case,reducing the output bit rate may not significantly reduce the userexperience and, if so, is judged acceptable. Next, the task is initiatedat the appropriate server.

Returning to FIG. 10, media provider request 1097, like request 1096,specifies on-demand transcoding, wherein the constraints identified inthe publishing service request can be varied before transcoding. Mediaprovider request 1097, however, is combined here with a kill taskscommand 1098, similar to command 1095 described above. This combinationcorresponds to publishing option 1065.

Finally, returning to FIG. 10, media provider request 1099 specifiespass-through processing and corresponds to publication option 1070.

E. Estimating Task Load

As discussed above, the media provider request processor can comprise atask load monitor that estimates the processing load imposed by a giventranscoding task. This estimation is necessary when determining whichtranscoding server will be assigned the task. The process for estimatingthe load associated with a transcode task is illustrated in FIG. 11.This process is performed with respect to each possible transcodingserver. In this manner, the task's load is determined with respect toeach server.

In step 1110, information is collected pertaining to the nature of therequired transcode task. In particular, this information includesproperties of the source and destination formats. This representsconsideration of format of the source media content, and the format ofthe requested media content. Step 1110 also includes determination oftranscoding server properties. This is necessary because the processingload created by a transcoding task depends in part on the properties ofa prospective transcoding server.

In step 1120, a search is performed over historical transcode load data,in an attempt to find the closest match for the transcode task at handwith respect to source, destination, and server properties. In step1130, the difference between the transcoding task at hand and theclosest match is determined. If, in step 1140, the match is sufficientlyclose, then in step 1150, it is assumed that the load of the task athand is approximately that of the closest historical match. The load ofthe historically matching task is therefore returned in step 1150.

If, in step 1140, the closest match is not sufficiently close to thetask at hand, then in step 1160, a conservative, fixed, predeterminedload estimate is returned.

In either case, the result of process 1100 is an estimate of the loadthat would be imposed by the task on a given transcoding server. Afterthis process is performed with respect to all possible transcodingservers, and after current server loads are determined (see Section III.F. below), a decision can be reached as to the server to which the taskshould be assigned.

F. Estimating Server Load

The media provider request processor can also comprise a server loadmonitor for determining the current processing load on any giventranscoding server. The process for this determination is illustrated inFIG. 12. In step 1210, the load on a transcoding server is determined bya direct measurement. In step 1220, a determination is made as towhether immature transcoding tasks exist at the server. Immaturetranscoding tasks represent tasks that have been initiated at atranscoding server, but are not yet using the processing capacity thatthey eventually will. If immature transcoding tasks exist, then, at step1230, the transcoding server load is determined to be the measured loadplus an estimated mature load for each as yet immature task. If, in step1220, no immature tasks are found to exist at the transcoded server,then, in step 1240, the measured load is returned. In one example, notintended to limit the scope of this invention, the measured load wouldbe expressed as a percentage of the available load. In the case of aWindows Media server, the load returned would be the current number ofstreams being served, divided by the maximum number of streams served.In the case of a transcoding server, the measured load could beexpressed as the percentage of the server's total CPU capacity currentlyallocated to the transcoding tasks. In an embodiment of the invention,each immature transcoding task reports to the server load monitor whenit has matured, i.e., when it starts using its maximum requiredprocessing capacity. In an embodiment of the invention, this reportingtakes place via the database. As discussed above, database coherencymust be maintained, so that any process that accesses the databasereceives accurate information. For this reason, steps must be taken toensure that updates to the database are completed before permitting anyattempts to read the data.

G. Speculative Batch Processing

Also as described above, media provider request scheduler can include aspeculative transcode manager. The process of speculatively issuing abatch media provider request is illustrated in FIG. 13. In step 1310, adetermination is made as to whether transcoding capacity is available.In an embodiment of the invention, this determination comprisesprocesses 1100 and 1200 described above. Process 1300 continues only ifsuch capacity is present. In step 1320, a determination is made as towhether any “pre-encodes” have been requested. Publishers, for example,may request batch processing in anticipation of future publishingservice requests; such publishers are therefore requesting“pre-encoding.” Such requests can be queued at the media providerrequest scheduler. If pre-encodes have been requested, then in step 1350a media provider request is issued, corresponding to the requestedpre-encode. If, in step 1320, it is determined that no pre-encodes havebeen explicitly requested, then in step 1330, transcode records arereviewed in order to predict future transcode requests. In step 1340, abatch media provider request is issued based on the prediction of step1330.

In one example not intended to limit the scope of this invention, thespeculative transcoding manager would re-encode a previouslyrealtime-transcoded content at slower than real-time in order togenerate a higher quality output. Techniques employed to generate higherquality output could also include allowing more time for decompressionand compression, filtering of the decompressed video and audio signals(e.g., noise reduction), and multipass encoding, to name a few.

In another example, the speculative transcoding manager would examineusage patterns for a particular piece of media content, and find thatusers had made numerous Real media requests at bit rates of 28.8 k, 128k, 300 k, but not at 56 k. In this case the lack of a 56 k transcodewould be seen as anomalous and, in reaction, the speculative transcodingmanager would spawn a request for the content at the 56 k bitrate.

In another example not intended to limit the scope of the invention, thespeculative transcoding manager would pre-transcode content based on apublisher's request. If for example, CNN produced daily content, CNNcould specify that their content is to be pre-transcoded in real time orslower than real time into Windows Media, Real, and QuickTime formats at56 k, 128 k, and 300 k. In doing this, CNN could guarantee theavailability of their content at the moment they published itexternally.

H. Zero-Downtime Reassignment of Servers to Different Tasks, FaultTolerance, and Zero-Downtime Server Retirement

A distributed on-demand media transcoding system according to thepresent invention can include pools of servers with differentcapabilities (e.g., transcoding servers, distribution servers servingmedia content in Real format, distribution servers serving media contentin a Windows Media format, distribution servers serving media content ina Quicktime format, distribution servers serving media content in agMovie format, etc.). In many implementations, these differences incapability are strictly due to installed software. So it is practical toreconfigure a server to perform a different task via automated softwarethat does not require operator intervention.

One variable, when optimizing the quality of service and efficiency of adistributed on-demand media transcoding system, is the allocation offarm servers to these varying tasks. Being able to reallocate availableservers on the fly to different tasks allows a media provider requestprocessor to adapt to changing usage patterns while maintaining the bestquality of service and efficiency. However, this is difficult to dowithout interrupting service. A related problem is that of faulttolerance and upgrade. If a server goes down unexpectedly, this must notinterrupt service in any other part of the farm. If a server needs to beretired so that it can be upgraded, this too must not interrupt service.

In one embodiment, illustrated in FIG. 14, fault tolerance and upgradeproblems are overcome as each server (including, but not limited to,transcoding servers and distribution servers) registers itself with thesystem in a database (such as database 843 of FIG. 8) when the server isavailable. In an embodiment of the invention, the database resides atthe media provider request processor. The registration informationincludes a list of the services which that server is configured toperform. The media provider request processor consults the database whenseeking machines to perform given tasks. In step 1405, this allowsdetermination as to whether a server's current registration informationhas been received. Each server is responsible for updating its entry inthe database at a fixed period. By ignoring servers which have failed toupdate their database entry within the fixed period, the media providerrequest processor can efficiently rule out most unavailable servers(step 1420) without needing to establish communication with them on eachquery. This saves significant processing and network bandwidth costs.

If the registration information for a server is current, then the serveris presumably available, as indicated in step 1410. In step 1415, themedia provider request processor then chooses a server from theremaining pool and performs application-level checks to verify that thechosen server is in fact usable. The media provider request processorrepeats this process until it finds a server it can use to satisfy theuser's request.

In an embodiment of the invention, each server supports a “shutdown”primitive which will cause it to remove its own entries from thedatabase, thus preventing the media provider request processor fromscheduling any new tasks on that server. Then, after all currentlyrunning tasks have completed, the server can be taken down withoutclient-visible interruption of service. This process is illustrated inFIG. 15. This shutdown primitive can be activated from an automatedsystem, simplifying the process of upgrading or reassigning a server. Instep 1505, a shutdown primitive is issued to the server. In step 1510,the server deletes its registration information from the database oncommand. In step 1520, any currently running tasks are allowed tocomplete. In step 1530, the server is taken down.

IV. DATA

As described above, the media transcoding system includes one or moretranscoding engines that convert certain types of media-content(referred to herein as a source type) to another type of media content(referred to herein as a destination type). Transcoding can involve anumber of different conversion operations. The particular conversionoperations used depend upon the media content and associated publishingvariables being converted. “Publishing variables” as used herein refersto different characteristics of media content.

According to the present invention, media content is digital data beingpublished over a network. In this case, publication refers to digitaldata which has been formatted for delivery over a network and forviewing by a destination media player. Publishing variables for mediacontent can include, but are not limited to, the file format, bit rate,communication protocol(s), physical medium, compression algorithm,and/or digital rights management information.

The digital data can be any type of file format including but notlimited to container formats, bitmap formats, video formats, audioformats, vector formats, metafile formats, scene formats, animationformats, multimedia formats, hybrid formats, hypertext and hypermediaformats, three-dimensional data (3D) formats, virtual reality modelinglanguage (VRML) formats, font formats (bitmap fonts, stroke fonts,spline-based outline fonts), page description language (PDL) formats,and any other type of graphics file format or other file format. Table Ilists examples of such file formats that can be used in embodiments ofthe present invention:

TABLE 1 Example File Formats Format Type ADOBE ILLUSTRATOR MetafileADOBE PHOTOSHOP Bitmap ATARI ST GRAPHICS FORMATS Bitmap and AnimationAUTOCAD DXF Vector AUTODESK 3D STUDIO Scene Description BDF BitmapBRL-CAD Other BUFR Other CALS RASTER Bitmap CGM Metafile CMU FORMATSMultimedia DKB Scene Description DORE RASTER FILE FORMAT Bitmap DPXBitmap DR. HALO Bitmap DVM MOVIE Animation ENCAPSULATED POSTSCRIPTMetafile (page description language) FACESAVER Bitmap FAX FORMATS BitmapFITS Other FLI Animation GEM RASTER Bitmap GEM VDI Metafile GIF BitmapGRASP Animation GRIB Other HARVARD GRAPHICS Metafile HIERARCHICAL DATAMetafile FORMAT IFF Bitmap IGES Other INSET PIX Bitmap INTEL DVIMultimedia JPEG FILE INTERCHANGE Bitmap FORMAT KODAK PHOTO CD BitmapKODAK YCC Bitmap LOTUS DIF Vector LOTUS PIC Vector LUMENA PAINT BitmapMACINTOSH PAINT Bitmap MACINTOSH PICT Metallic MICROSOFT PAINT BitmapMICROSOFT RIFF Multimedia MICROSOFT RTF Metafile MICROSOFT SYLK VectorMICROSOFT WINDOWS Bitmap BITMAP MICROSOFT WINDOWS Metafile METAFILE MIFFBitmap MPEG Other MTV Scene Description NAPLPS Metafile NFF SceneDescription OFF Scene Description OS/2 BITMAP Bitmap P3D SceneDescription PBM., PGM., PNM., and PPM. Bitmap PCX Bitmap PDS OtherPICTOR PC PAINT Bitmap PIXAR RIB Scene Description PLOT-10 Vector PNGBitmap POV Vector PRESENTATION MANAGER Metafile METAFILE PRT SceneDescription QRT Scene Description QUICK TIME Other RADIANCE SceneDcsenption RAYSHADE Scene Description RIX Bitmap RTRACE SceneDescription SAF Bitmap and other SENSE8 NFF Scene Description SGI IMAGEFILE FORMAT Bitmap SGI INVENTOR Scene Description SGI YAODL SceneDescription SGO Vector SPIFF Bitmap SUN ICON Bitmap SUN RASTER BitmapTDDD Vector and Animation TGA Bitmap TIFF Bitmap TTDDD Vector andAnimation URAY Scene Description UTAH RLE Bitmap VICAR2 Bitmap VIFFBitmap VIS-5D Vector VIVID AND BOB Scene Description WAVEFRONT OBJVector WAVEFRONT RLA Bitmap WORDPERFECT GRAPHICS Metafile METAFILE XBMBitmap XPM Bitmap XWD Bitmap ZBR Metafile

See, Murray and vanRyper, pp. 12-26. These examples are illustrative andnot intended to necessarily limit the present invention. Other fileformats (now known or developed in the future) can be used as would beapparent to a person skilled in the art given this description.

Even within the same file format, digital data can be compressedaccording to different compression algorithms. In a QUICK TIME formattedfile, for example, video can be compressed in accordance with H.263,CINEPAK, JPEG, QT ANIMATION, or QT VIDEO standards. As a furtherexample, in a WINDOWS MEDIA ASP formatted file, audio can be compressedin accordance with the MICROSOFT AUDIO FORMAT, ACELP, VOXWARE, or MP3standards. Compression algorithm choices can be made based onoptimization according to bit-rate choices, or according to the natureof the content. For example, video files in which little motion occurs(“talking heads”) and video files in which there is a substantial amountof motion (“high-motion” video) may each be more efficiently compressedusing different compression algorithms.

Within any one compression algorithm, there can be further variations.For example, files compressed according to the JPEG standard can beeither YUB-based or RGB-based,

In addition to the publishing variables set forth above, there are alsopublishing variables unique to video data and audio data. Publishingvariables for video data include the width and height of the video imagein pixels as well as the frame rate of the video. Depending on thebit-rate requirements and the nature of the data, different settings maybe necessary in order to ensure the best picture quality. For example,some video may be better viewed at 15 frames per second at 160×120pixels, while some others may be better viewed at 5 frames per second at320×240 pixels, even at the same bit-rate. Where the bit-rate is 56Kbps, picture quality becomes very limited, and it is almost neveroptimal to deliver video in 640×480 pixel resolution. Yet anotherpublishing variable for video data is the number of bits per component.

Publishing variables for audio data include the number of samples persecond, the number of channels (e.g., mono, stereo, 5-channel) and thesample size (8-bit, 16-bit, etc.). Different settings may be necessaryto ensure audio quality in light of a particular content type andbit-rate.

Publishing variables may also include the size of data packets beingsent and the choice of transmission protocol (e.g., TCP vs. UDP).

Transcoding can therefore be viewed as conversion of data having asource type (defined by a set of publishing variables) to data having adestination type (defined by a second set of publishing variables).Examples are shown in the following tables:

Tables 2-5: Example Transcoder Operations

TABLE 2 Publishing Variables Source Type Destination Type physicalmedium Disk Network communication protocol(s) File I/O RTSP containerformat MPEG1 QUICK TIME encoding MPEG1 SORENSON (video) QDESIGN (audio)bit rate 1.5 Mbps 300 kbps

TABLE 3 Publishing Variables Source Type Destination Type physicalmedium Wired Network Wireless Network communication protocol(s) HTTP MMScontainer format MPEG1 WINDOWS MEDIA encoding MPEG1 MPEG4 (video)MSAUDIO (audio) bit rate 1.5 Mbps 100 kbps

TABLE 4 Publishing Variables Source Type Destination Type physicalmedium Wired Network Wired Network communication protocol(s) HTTP RTSPcontainer format QUICK TIME REAL encoding H.263 REAL PROPRIETARY G2Video/Audio bit rate 56 kbps 56 kbps

TABLE 5 Publishing Variables Source Type Destination Type physicalmedium Disk Wireless Network communication protocol(s) File I/O HTTPcontainer format MPEG 1 MP3 Encoding MPEG 1 audio only-MP3 bit rate 1.5Mbps 16 kbps

These examples are illustrative and not intended to limit the presentinvention. Other types of on-demand transcoding operations that areknown now or developed in the future can be used as would be apparent toa person skilled in the art given this description.

V. CONCLUSION

The foregoing description of the specific embodiments will so fullyreveal the general nature of the invention that others can, by applyingknowledge within the skill of the art (including the contents of thereferences cited herein), readily modify and/or adapt for variousapplications such specific embodiments, without undue experimentation,without departing from the general concept of the present invention.Therefore, such adaptations and modifications are intended to be withinthe meaning and range of equivalents of the disclosed embodiments, basedon the teaching and guidance presented herein. It is to be understoodthat the phraseology or terminology herein is for the purpose ofdescription and not of limitation, such that the terminology orphraseology of the present specification is to be interpreted by theskilled artisan in light of the teachings and guidance presented herein,in combination with the knowledge of one of ordinary skill in the art.

What is claimed is:
 1. A system for publishing transcoded media content,comprising: a publishing service request processor that generates amedia provider request based on a requesting client's publishing servicerequest; and a media provider farm that receives said media providerrequest from said publishing service request processor and deliverstranscoded media content to fulfill said media provider request.